Differences between Real-Time PCR and Rapid Diagnostic Test

Rapid Diagnostic Test vs Real-Time PCR (qPCR)

There are several diagnostic tests that have been authorized for Emergency Use by the FDA for diagnosis of a wide range of infections. Notably, these diagnostic tests aim at identifying an infected individual from a non-infected person, using different working principles and duration for the tests vary. Diagnostic tests can be molecular-based or immuno-assays.

The most common tests are:

Rapid Diagnostic tests

• They are mainly serological tests principally working to detect immune reactive elements i.e antibodies or detecting the pathogenic antigens.
• They are mainly used for screening of diseases, and at a health care worker’s convinces hence, the are point-of-care diagnostic tests

Real-Time PCR (qPCR)

• This is a molecular-based technique that principally works to qualitatively detect the presence of pathogen genome i.e RNA or DNA.
• The genome undergoes different stages of processing before identification followed by sequencing for classification of the pathogen strains.

Differences between the Rapid Diagnostic Test and Real-Time PCR (qPCR)

Features	Rapid Diagnostic Test	Real-Time PCR (qPCR)
Sample	They require whole blood or plasma or serum samples for tests or biopsy.	The test uses liquid or solid samples depending on the condition of the test e.g Respiratory infection requires nasal swabs or nasopharyngeal swabs.
Principle	Qualitative and semi-qualitative in-vitro devices.	Qualitative and quantitative in-vitro medical devices.
Types	Rapid Antibody test Rapid Antigen test	quantitative real-time PCR semi-quantitative real-time PCR
Objectivity	The test aims at identifying and/or detecting antibodies, majorly IgG and/or IgM. OR Detection of antigens (pathogen particles ) in blood.	The test aims at amplifying and detecting the pathogen genome (RNA and DNA).
Duration of Test	It takes approximately 15 minutes to 2 hours to get the test result.	It can take 1 hour to 48 hours to get the test result.
Reagents	The test uses a solution buffer to allow the capillary tube.	Several PCR reagents are used.
Instrumentation	It is a simple chromatographic capillary tube.	It is complex with several compartments each performing a series of protocols.
Procedure	Most are one-step procedures.	They involved a series of steps including denaturation, annealing, and extension.
Platforms	Lateral flow tests Agglutination Dipstick Microfluidics	High-throughput platforms which include Dynamic Array Chip, TaqMan Open array, and SmartChip.
Sensitivity and specificity	Most have high sensitivity >95% and specificity of >99%.	The sensitivity of most tests ranges from >95% and specificity of >83%.
Applications	– Used for preliminary or emergency medical screening. – Used in point-of-care testing for diagnosis. – Used for diagnosis of a wide range of diseases including Malaria, HIV, TB, Influenza, Dengue fever, Strep B, Syphilis, COVID-19.	– Research Applications – Genetic cloning – Genetic disease diagnosis – Cancer detection
Results	A positive test indicates the presence of Antibodies against the specific pathogen or presence of antigens of the pathogen. A negative test indicates the absence of antibodies produced against the pathogen or absence of pathogenic antigens.	Positive results indicate the detection of pathogen genome RNA/DNA and negative results indicate a lack of RNA/DNA genome.
Portability and Cost	They are small and easily portable and inexpensive.	Most are large machines difficult to move from one place to another and they are expensive to manufacture and purchase.
Examples	Rapid HIV Test Rapid Plasma Reagin Rapid Influenza Diagnostic Test Malaria Antigen Detection Test Rapid Strep B Test Rapid Urease test Rapid Dengue test Syphilis Rapid Test Tuberculosis IgM/IgG Rapid test COVID-19 IgG/IgM Rapid Test	COVID-19 RT-qPCR Influenza Real-Time PCR Parasitic Real-Time PCR Fungal Real-Time PCR Bacterial Real-Time PCR

References and Sources

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1860455/
2. https://www.researchgate.net/figure/The-relationship-between-rapid-diagnostic-test-RDT-and-polymerase-chain-reaction-PCR_fig2_285595052
3. https://www.intechopen.com/books/polymerase-chain-reaction-for-biomedical-applications/high-throughput-platforms-in-real-time-pcr-and-applications
4. https://www.indiatvnews.com/news/india/real-time-pcr-test-vs-anti-body-test-what-is-india-s-coronavirus-testing-strategy-608900
5. https://www.indiatoday.in/india/story/how-rapid-antibody-tests-are-different-from-existing-pcr-tests-for-covid-19-explained-1663441-2020-04-05